Monzon had a very effective 1-2....and intricate part of his offensive arsenal....and he didn't miss with it.
It's funny now that i think about it even though the 1-2 is the most basic and fundamental combo everyone and their mom knows and it's one of the first things they teach you, not a lot of fighters are particularly "great" at that combination. Weird. Wladmir had a hell of a 1-2 down the pipe when he let his hands go. Holyfield was a swiss army knife and could throw nearly any punch or combination with excellent form. The 1-2 Maidana used on Mayweather in their 2nd fight was beautiful. Nearly had him out of there before the bell.
Hearns jab to the body followed by that right cross...... Just ask Duran. But you can't go wrong with Louis, M.Spinks (at Lt.heavy), Ali, Holmes, Lewis,Arguello,Monzon, Little Red Lopez, R.Mayweather.
Yeah my first thought was Hearns. Second thought was Ali. Next was Monzon. Ground covered already. After trying to think of an original pick, I'll say Ellis. He sure believed in those punches and used them to good effect.